JPH08316918A - Transmission method for intra-pipe radio wave - Google Patents

Abstract

PURPOSE: To provide a method which can optionally select a reaching range of the radio wave and therefore can transmit the radio wave to only the pipe that is checked by changing the frequency to be sent into the pipe in response to the cut-off frequency of the pipe. CONSTITUTION: A robot 3 is provided with a self-traveling device having wheels and a device which photographs the inside of a gas pipe 5. The robot 3 is controlled by the radio wave sent from a ground check device 1 and sends back the photographed images onto the ground to display them on a monitor 6. The cut-off frequency of the transmitted radio wave is regulated by a specific expression and decided by the inner diameter of the pipe 5. The decided frequency is selected and such radio waves are applied to the ground control of the robot 3 and also to the transmission of images from the robot 3. Thus radio wave can be smoothly transmitted in the pipe 5 and the smooth communication is secured with the robot 3. On the other hand, the radio wave is not transmitted in a slender pipe 4 since the frequency of the radio wave transmitted in the pipe 5 is less than the cut-off frequency of the pipe 4. Therefore, the radio wave is never sent into a home, etc., from an end part of the pipe 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transmitting radio waves in a pipe which can selectively transmit radio waves to a desired pipe.

[0002]

2. Description of the Related Art For example, in a gas pipe for supplying a gas to a consumer, a large number of gas pipes are provided between the supply side and the consumer, which is suitable for preventing cracks and breakage of the pipe. Accurate inspection is required. Also in chemical plants and the like, pipes for transporting various fluids are arranged and appropriate inspection is required.

By the way, it takes a lot of time and labor to excavate a pipe buried in the ground and inspect the condition of the pipe.
It is economically impossible to inspect every pipe. In addition, it is very difficult to directly observe the inside and visually inspect a long pipe that is complicatedly piped.

Various methods are known as methods for inspecting such gas pipes and pipes carrying various other fluids. The present inventors have made a robot run inside the pipes,
Damage to the pipe by taking a picture of the inside of the pipe by an imaging device mounted on the robot and inspecting the condition inside the pipe on the ground, or by transmitting radio waves inside the pipe and receiving radio waves leaking from the damaged part to the outside of the pipe Have invented a method for detecting the like.

[0005]

However, when a radio wave is sent into the pipe for communication with a robot or to leak from a damaged portion of the pipe, the radio wave may propagate in the pipe and may be radiated from an unscheduled place. . In other words, if a household appliance is attached to the end of the pipe, radio waves are emitted from the pipe end, and if the pipe has an open end, it is emitted from there. Then, when a radio wave is disturbed in the home, or when communication or power supply is performed with microwaves, electromagnetic waves cause a problem to the human body. Also, when leaks of radio waves are detected for inspection of pipes, it is erroneously determined that there is divergence from these unplanned places as damaged parts of the pipes, making it difficult to determine the place where the radio waves leak. there were.

The present invention solves the above-mentioned problems and prevents radio waves from unnecessarily leaking by selectively allowing radio waves to reach a desired pipe, thereby preventing radio wave interference and easily identifying a damaged portion. The purpose is to provide a transmission method of.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a pipe network in which pipes having different diameters are connected, in which the frequency of the radio wave transmitted from one end of the pipe to the inside of the pipe reaches the radio wave. The transmission method of the in-pipe radio wave is configured so as to be equal to or higher than the desired cutoff frequency of the tube and equal to or lower than the cutoff frequency of the tube where the arrival of the radio wave is not desired.

Further, the pipe network is a gas pipe, and the cutoff frequency of the diameter of the pipe connected to each consumer is set to be equal to or lower than the cutoff frequency, and the frequency of the radio wave is set so that the radio wave does not reach the pipe connected to the consumer. did.

The radio waves are to be communicated with the robot inserted in the pipe.

The radio wave is a radio wave that leaks from a damaged portion of the pipe and is used in a detection method for detecting the damaged portion of the pipe by detecting the leaked radio wave.

[0011]

The cutoff frequency is a predetermined frequency determined from the inner diameter of the tube, and is the lowest frequency that can propagate in the tube with a small amount of attenuation. That is, when the frequency is equal to or lower than the cutoff frequency, even if the radio wave is transmitted into the pipe, the attenuation is large and the radio wave does not travel far.

A general gas pipe network sends gas from a supply side such as a gas company using a pipe having a large diameter, divides the gas into many pipes on the way, and gradually makes the pipe thinner, thereby making it a final consumer. Most households, except for some large consumers, are supplied with gas pipes with a diameter of 27.6 mm.

Therefore, for example, when the robot is advanced inside the gas pipe and the robot is made to perform a work such as photographing inside the pipe, the pipe to be inspected by the robot for the frequency of radio waves exchanged with the robot. Above the cut-off frequency, and below the cut-off frequency for household pipes. With this setting, the radio waves can be reliably propagated inside the tube in which the robot is inserted, that is, the tube with a relatively large diameter, and the robot can be wirelessly controlled inside the tube, while the tube with a small diameter can be blocked. The radio wave does not proceed because it is below the frequency.
Therefore, even if a thin pipe for home use is connected to the pipe where the robot is working, radio waves do not enter the pipe for home use, so radio waves for robot communication pass through the pipe for home use. It is never released into the home.

Further, in the work of transmitting a radio wave into the pipe and detecting the radio wave leaking from the damaged portion of the pipe to detect the damaged portion of the pipe, the inspection is performed at the cutoff frequency of the pipe for which damage is to be detected or higher. It emits at frequencies below the cutoff frequency of the thinner tubes connected to it. That is, when pipes having different diameters are sequentially connected, the transmission frequency is changed stepwise for each cutoff frequency for inspection. For example, first, a frequency is set in a range that is equal to or higher than the cutoff frequency of the pipe having the maximum diameter and is equal to or lower than the cutoff frequency of the pipe having a smaller diameter, and the radio wave is transmitted into the pipe. Then, the radio wave propagates only in the pipe of the maximum diameter, does not enter the pipe of the next diameter, and the leak of the radio wave in the pipe of the maximum diameter can be inspected. Then, the inspection range is expanded by sequentially increasing the frequency. By doing this, in addition to preventing radio waves from leaking into the home as described above, radio waves propagate in a pipe with a low cut-off frequency of the pipe, that is, a pipe with a large diameter, and if the pipe is damaged, it can be easily detected. On the other hand, since the radio wave does not propagate to the pipe whose cutoff frequency is higher than the transmission frequency, the radio wave can reach only the desired pipe and the radio wave reach range can be specified to limit the inspection range where the radio wave should be detected. Can be easily confirmed and a reliable damage inspection can be performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method of transmitting radio waves in a pipe according to the present invention will be described with reference to FIG. 1, taking as an example a case where a wirelessly controlled robot is operated in a pipe.

The robot 3 is equipped with a self-propelled device having wheels and a photographing device for photographing the inside of the tube 5 (neither of which is shown). The robot 3 is controlled by radio waves transmitted from the inspection device 1 on the ground and also photographs. The image is sent back to the ground wirelessly,
The image is displayed on the monitor 6. The pipe to be inspected is a gas pipe 5 which is usually called 150A and has a diameter of 155.2 mm, and has a sufficient thickness to allow the robot 3 to be inserted, and the inspection device 1 is connected to the pipe end via the antenna 2. ing. The antenna 2 is shown in FIG.
As shown in FIG. 5, it has a bottomed cylindrical shape that fits into the gas pipe 5, and is provided with a transmitting antenna 21, a receiving antenna 23, and position detecting antennas 22 and 24 at the central portion and peripheral portion of the bottom. The robot 3 is appropriately provided with an antenna corresponding to these antennas. The gas pipe 5 has a diameter of 2
A 7.6 mm household thin tube 4 called 25A is connected, and the thin tube 4 is connected to each appliance of each consumer who is a consumer.

The cutoff frequency of the tube is calculated by the following equation 1.

[0018]

## EQU1 ## Cutoff frequency = speed of light / (1.706 × inner diameter) The relationship between the inner diameter of the tube and the cutoff frequency is shown in FIG.

Therefore, the cutoff frequency of the gas pipe 5 of 150 A is

Based on [Equation 1], the frequency becomes 1.13 GHz, and the thin tube 4
The cutoff frequency of is calculated as 6.37 GHz. For communication with the robot 3 in the pipe, the frequency is set to 3 GHz under the condition that a frequency higher than the cut-off frequency of the gas pipe 5 and lower than the cut-off frequency of the narrow pipe 4 is selected. If the selected frequency is too close to the cutoff frequency, the attenuation will be slightly higher, so it is preferable to separate it from the cutoff frequency.

By selecting the frequency in this way and using the radio wave of the selected frequency for controlling the robot 3 from the ground and transmitting the image from the robot 3, the radio wave is satisfactorily transmitted inside the gas pipe 5, Communication with 3 can be performed without any trouble. On the other hand, in the thin tube 4, since the frequency of the radio wave transmitted in the tube 5 and the frequency of 3 GHz are below the cut-off frequency of the tube 4, the radio wave does not enter the tube 4 and the home portion is discharged from the end of the thin tube 4. Radio waves are not emitted inside.

Next, another embodiment will be described.

In this example, radio waves are transmitted to the inside of the pipe to be inspected, and when there is a damaged portion in the pipe to be inspected, the radio wave leaks from this damaged portion, and the leaked radio wave is detected from outside the pipe. It is used for the inspection method to detect the damaged position of the pipe.

That is, an antenna is provided at one end of the pipe to be inspected, and a radio wave is transmitted from this antenna into the pipe, while a receiver for receiving the radio wave is provided outside the pipe to receive the radio wave while moving along the pipe. . If the pipe is damaged, radio waves leak out from the damaged part, so the damaged part is detected by receiving the leaked radio wave by the receiver.

FIG. 3 shows a pipe to be inspected in such an example. The pipe to be inspected is a gas pipe as in the above embodiment, and has a diameter of 155.
2 mm pipe 11 (150 A) and 105.3 mm diameter pipe 1
2 (100A) is connected, and the pipe 12 is connected to a 52.9 mm pipe 13 (50A), and each pipe 1
Household thin tubes 4 (27.6 mm, 25)
A) is connected. In practice, the tube is more branched, but omitted. Each of the tubes 11, 12 and 13 has an appropriate length, and the antenna 2 of the transmitter 20 is attached to one end of the tube 11.

First, when inspecting the pipe 11 for damage, the pipe 1
The cutoff frequency of 1 is 1.13 GHz or higher and the cutoff frequency of the tube 12 is 1.67 GHz or lower, and a frequency is selected as a transmission radio wave, which is transmitted from the transmitter 20 into the tube 11 through the antenna 2. . In this way, the pipe 11
Since the radio waves propagate inside, if the pipe 11 is damaged, the radio waves leak from the damaged part and the receiver (not shown) receives the radio waves from the damaged part to detect the position. it can. Since this radio wave is below the cutoff frequency of the tubes 12 and the thin tubes 4, it does not enter these tubes,
The detection range of radio waves by the receiver can be limited to only the tube 11. Moreover, since the radio wave does not leak from the end of the thin tube 4 or the like, no radio interference occurs in the home, and the radio wave leaking from the thin tube 4 does not cause a malfunction of the receiver, and an accurate damage inspection can be performed.

Next, the cutoff frequency of the tube 12 is set to 1.6.
Above 7 GHz, the cutoff frequency of the tube 13 is 3.33 G
Set in the range below Hz. In this way, the radio waves enter the pipes 11 and 12, but do not enter the pipes 13, the thin tubes 4, etc., so that the reach of the radio waves can be limited to the pipes 11 and 12, and the radio waves from the thin pipes 4 can reach. Can be prevented from leaking and accurate inspection can be performed without waste. Further, the frequency is set in the range of the cutoff frequency of the tube 13 of 3.33 GHz or more and the cutoff frequency of the thin tube 4 of 6.37 GHz or less. Then, thin tube 4
The radio wave can be transmitted to the entire tube except for the inspection, and the radio wave is not leaked from the thin tube 4.

As described above, since the pipe to be propagated can be changed by sequentially changing the transmission frequency, it is possible to specify the detection range and perform an accurate inspection. Further, since the radio wave is below the cut-off frequency of the thin tube 4, it does not enter the thin tube 4, and there is no malfunction such that the radio wave from the thin tube 4 is erroneously detected or radio interference is caused at home.

The pipe to be inspected is not limited to the gas pipe, but may be a pipe for carrying other fluids such as those used in plants. Further, the radio wave is not a signal used for control or the like, but may be a microwave having a large output for supplying electric power.

[0029]

According to the method of transmitting radio waves in a pipe of the present invention,
Since the frequency of the radio wave transmitted in the pipe is changed according to the cutoff frequency of the pipe, the reach range of the radio wave can be arbitrarily selected. Therefore, the radio wave is sent only to the pipe to be inspected, and the radio wave is not transmitted to other pipes, especially household pipes, so that it is possible to prevent the occurrence of radio wave interference at a portion equipped with a device or the like.

Further, in the inspection method for inspecting the pipe from the leakage of the radio wave transmitted to the inside of the pipe, since the reach range of the radio wave can be specified by utilizing the difference in the diameter of the pipe, the leaked radio wave is limited to only the specified transmission range. It suffices to conduct an inspection, and an accurate pipe inspection can be performed easily and surely in a short time. or,
Since there is no radio wave leaking from the open end of other pipes, the receiver does not receive radio waves from a place unrelated to damage, and does not detect the wrong position as a damaged place,
Accurate inspection can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a method of transmitting radio waves in a pipe according to the present invention.

FIG. 2 is a graph showing a relationship between a cutoff frequency and an inner diameter of a tube.

FIG. 3 is a diagram showing another embodiment of the in-pipe radio wave transmission method according to the present invention.

FIG. 4 is a diagram showing an antenna.

[Explanation of symbols]

 1 Inspection Device 2 Antenna 3 Robot 4 Capillary Tube 5 Gas Tube 6 Monitor 11, 12, 13 Tube 20 Transmitter 21 Transmitter Antenna 22, 24 Antenna 23 Received Antenna

Claims (4)

[Claims] 1. In a piping network in which pipes having different diameters are connected, the frequency of a radio wave transmitted from one end of the pipe into the pipe is set to be equal to or higher than a cutoff frequency of the pipe desired to reach the radio wave.
A method of transmitting radio waves in a tube, wherein the cutoff frequency of the tube that does not want the radio waves to reach is set to be equal to or lower than the cutoff frequency. 2. The pipe network is a gas pipe, and the frequency of the radio wave is set to be equal to or lower than the cutoff frequency of the pipe connected to each consumer, and the radio wave is prevented from reaching the pipe connected to the consumer. The radio wave transmission method according to claim 1, wherein the frequency of the radio wave is set. 3. The in-pipe radio wave transmission method according to claim 1, wherein the radio wave is a radio wave communicated with a robot inserted in the pipe. 4. The radio wave is a radio wave leaking from a hole formed in the pipe and used for a detecting means for detecting a damaged portion of the pipe by detecting the leaked radio wave.
Alternatively, the method of transmitting radio waves in a pipe according to item 2.